There are methods using patterns of edges and light and shade of a face for detecting positions of eyes. For example, a known facial parts abstracting device described in JPH10 (1998)-307923A creates a histogram by projecting darker portion of light and shade in a horizontal direction in order to obtain positions of eyes and eyebrows, and determines positions of the eyes and the eyebrows on the basis of configuration of the histogram. The facial parts abstracting device abstracts eyes, eyebrows, and a mouth by utilizing that peaks appeared in the histogram corresponding to portions such as the eyes, the eyebrows, and the mouth by creating the histogram.
A known eye position and face position detection device for stably detecting positions of eyes and a face is described in JP2000-339476A. With the known eye position and face position detection device, the center of a face is estimated on the basis of vertical edges histogram, right and left ends of the face is estimated on the basis of position of the center of the face, and histograms are created by projecting horizontal edges and vertical and horizontal edges in the horizontal direction within a range of the estimated right and left ends of the face. Accordingly, peaks appear at positions of eyes and eyebrows, and thus the eyes and the eyebrows are detected.
Notwithstanding, according to the known devices described in JPH10 (1998)-307923A and JP2000-339476A, peaks of a histogram different from peaks corresponding to the eyes and eyebrows appear around the eyes in case a driver wears glasses, and thus a position of eyes and eyebrows cannot be detected accurately. Similar problems are raised in case shade is reflected in the face when using a grayscale picture.
It is a condition for the known devices described in JPH10 (1998)-307923A and JP2000-339476A that a position of a face is approximately identified. However, in case a position of a face is off, accurate positions of eyes and eyebrows are unlikely detected because excessive peaks of a histogram other than the eyes and eyebrows appear or peaks are unreadable by the background.
Further, with the facial parts abstracting device according to JPH10 (1998)-307923A, a nostril is detected in order to specify a position of a face. However, because an image-capturing device has to be positioned below a face of an objective person in order to detect the nostril, setting location of the image-capturing device is limited.
With the eye position and face position detection device described in JP2000-339476A, the center of a face is detected first from the histogram of the vertical edges for detecting the position of the face. However, there is a drawback that an accurate position of a face is unlikely detected because it is difficult to identify the center of the face from vertical edges of a nose and glasses, or the like.
A need thus exists for a facial parts position detection device, a method for detecting facial parts position, and a program for detecting facial parts position, which securely detects position of facial parts without being influenced by conditions of objective person for detection.